Citing GMT: Place Zenodo DOI badge in the same line as the version text

[yvonnefroehlich]

Extending #163, trying to place the Zenodo DOI badges of the single releases in the same line as the related version text.

Currently the badge is added in a new line, which looks not optimal:

currently	aligned indent	coverted to a table

[seisman]

Preview tells that it still doesn't work. Since Sphinx supports both Markdown and ReST. Maybe it's easier to switch index.rst to index.md instead?

[yvonnefroehlich]

Preview tells that it still doesn't work.

I added blank lines before the badge line. Now, at least the indent is correct.

Since Sphinx supports both Markdown and ReST. Maybe it's easier to switch index.rst to index.md instead?

I tried this locally but so far I did not manage that the badge image is displayed correctly.

[yvonnefroehlich]

So, I found that using a table can be helpful here. With these changes it get this:

I could also add the bold style to the version numbers to be consistent with the list for the papers.

@seisman what do you think?